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Committed Information Rate
The committed information rate (CIR) for a queue performs two distinct functions:
1. Minimum bandwidth guarantees — ueues CIR setting provides the bandwidth which will be
given to this queue as compared to other queues on the port competing for a share of the
available link bandwidth. The queue CIR does not necessarily guarantee bandwidth in all
scenarios and also depends on factors such as CIR oversubscription and link port bandwidth
capacity. For each packet in an egress queue, the CIR is checked with the current transmis-
sion rate of the queue. If the current rate is at or below the CIR threshold, the queue is consid-
ered in-profile. If the current rate is above the threshold, the queue is considered out-of-
profile. This in and out profile state of queue is linked to scheduler prioritizing behavior as
discussed below.
2. Scheduler queue priority metric — The scheduler serving a group of egress queues prioritizes
individual queues based on their current CIR and PIR states. Queues operating below their
CIR are always served before those queues operating at or above their CIR.
Queues at the egress never marks the packets as in-profile or out-profile based on the queue CIR,
PIR values. The in-profile and out-profile state of the queue interacts with the scheduler
mechanism and provides the minimum and maximum bandwidth guarantees.
When defining the CIR for a queue, the value specified is the administrative CIR for the queue.
The user has some control over how the administrative CIR is converted to an operational CIR
should the hardware not support the exact CIR and PIR combination specified. The interpretation
of the administrative CIR is discussed below in
Although the 7210 SAS is flexible in how the CIR can be configured, there are conventional
ranges for the CIR based on the forwarding class of a queue. A queue associated with the high-
priority class normally has the CIR threshold equal to the PIR rate although the 7210 SAS allows
the CIR to be provisioned to any rate below the PIR should this behavior be required.
The CIR for a queue is provisioned on egress within service egress QOS policy.
The CIR for the network queues are defined within network queue policies based on the
forwarding class. The CIR for the network queues is specified as a percentage of the network
interface bandwidth.
7210 SAS-X and 7210 SAS-R6 OS Quality of Service Guide
Adaptation Rulefor Queues on page 41
QoS Policies
Page 39
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